We are investigating gene expression in nervous tissue using as tools steroid hormones which regulate pituitary function and influence behavior by interacting directly with the nervous system. Our approach emphasizes the fate of the hormones themselves: entry into the brain, intracellular conversion to more or less active metabolites, binding to soluble intracellular receptor sites, and transfer to the cell nucleus. We are also studying the possible inductive effects of steroid hormones on brain enzymes and on a receptor for progestins which may be involved in activation of sexual behavior and the preoculatory LH surge. We are also studying developmental aspects of these steroid-brain interactions with two specific aims: 1) The oncogeny of hormone receptors in brain relative to the development of functional neural systems which these hormones are known to influence; 2) Investigating biochemically and pharmacologically the mechanism of the organizing influences of androgen on the fetal and neonatal brain. Autoradiography and a variety of other cell biological and neurochemical techniques are being employed.